The maximum score the game gives you is 99999 before it resets back to 0. This will change the speed of the dinosaur to 6000. You can use any other number. Try writing the speed to -1  it will make the dinosaur to go backward and the entire game scene follows its backward movement.

Once you reach that score, the game essentially becomes an endless runner, with no further changes in gameplay. After 99999 score, the dino game resets your score back to 0 but the speed is set to 6000. And, this happens every time you reach 99999 score.